added try/except blocks in site delete view
added try/except blocks in site delete view

fixes issue when trying to delete a site that is associated with a
sampling feature that does not exist. This should only occur in
development when the `dataloader` db does not match with the `odm2` db
because the two databases were not copied over at the same time.

ODM2/ODM2WebSDL,ODM2/ODM2WebSDL,ODM2/ODM2WebSDL